With the recent spread of artificial cultivation of mushrooms, they are now supplied abundantly. However, a satisfactory method of cultivation has not been established although various improvements have been made.
In general, in artificial cultivation of mushrooms, the fungal bed exerts great influences on the yield and quality of the mushrooms. Thus, many investigations have been made on the method of cultivation. For example, the present inventors have discovered that in artificial cultivation of mushrooms growing on the fungal bed only, such as Flammulinaa velupipes Karst, Lyophyllum aggregatum, and Pholipa nameko S. Itoh et Imai, addition of water-absorbing polymeric substances to the fungal bed produces excellent effects (see
Japanese Patent Application (OPI) No. 212722/83) (the term "OPI" as used herein refers to a "published unexamined Japanese patent application", hereinafter the same).
It is known, however, that in artificial cultivation of mushrooms, such as Agaricus campestris, requiring a fungal bed and a covering soil, unlike the artificial cultivation of Flammulinaa velupipes Karst, etc., the covering soil as well as the fungal bed exert great influences on stabilization of cultivation, yield, and quality (e.g., form, size, etc.) and, therefore, the proper choice of the covering soil and fungal bed is of great importance. It has been desired to develop a method of cultivation which permits stable production of high quality mushrooms in high yields.
In artificial cultivation of these mushrooms requiring the fungal bed and covering soil, it is said that the covering soil not only prevents abrupt changes in the temperature and humidity of the inner part of the fungal bed, thereby protecting mycelia, but also accelerates the formation of fruit body primodia by the physical and chemical action of soil (e.g., retention of gases, multiplication of microorganisms, retention of water, passage of air, etc.). Therefore, a suitable covering soil is such as to permit easy passage of air and also to have a proper water-retention capability, which are essential for the growth of mycelia and the differentiation and growth of fruit body primodia.
An example of the covering soil satisfying the above-described requirements is a clay loam soil (clay content, about 40%). This kind of soil, however, when used as a covering soil, suffers from disadvantages in that the aggregate structure of soil is gradually broken by repeated water-spray, resulting in a reduction in air-permeability and water-retention of the soil and, thus, the formation of emergence of fruit body is reduced, leading to a drop in yield.
Peatmoss is relatively superior in water-retention, but its air-permeability is too high. When, therefore, peatmoss is used as a covering soil, the formation of fruit body occurs excessively and, therefore, high quality mushrooms cannot be obtained unless thinning is applied at the time of the emergence of fruit body. Moreover, the harvest time is shortened and the yield drops.
In order to eliminate the above-described problems, an improved method has been proposed in which a small amount of peatmoss is added to soil. This method, however, fails to completely overcome the problems. Thus, at the present time, there is not available a method of cultivation which permits stable production of high quality mushrooms in high yields.